U.S. patent number 7,292,940 [Application Number 10/784,201] was granted by the patent office on 2007-11-06 for vehicle control system.
This patent grant is currently assigned to DENSO CORPORATION. Invention is credited to Akira Isogai, Takao Nishimura, Eiji Teramura.
United States Patent |
7,292,940 |
Isogai , et al. |
November 6, 2007 |
Vehicle control system
Abstract
In a vehicle control system performing collision avoiding
control when a collision with a preceding vehicle cannot be avoided
by normal running condition control, driving safety is improved by
prompting a driver to intervene in the vehicle's control in a
reliable manner. When a set switch is turned on in the "cancel"
state, the transition to the "in-control, inter-vehicle distance
control" sub-state occurs and an inter-vehicle distance control is
performed. If a collision with a preceding vehicle cannot be
avoided by the inter-vehicle distance control (if the collision
alarm flag XA=1), transition to the "in-control, collision alarm"
sub-state occurs and a collision alarm is generated. If the
acceleration required for avoiding collision is further increased
(if the collision avoiding control flag XC=1), the state transits
to the "in-control, collision avoiding control" sub-state, and a
collision avoiding control is performed.
Inventors: |
Isogai; Akira (Anjo,
JP), Teramura; Eiji (Okazaki, JP),
Nishimura; Takao (Nagoya, JP) |
Assignee: |
DENSO CORPORATION (Kariya,
JP)
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Family
ID: |
32821112 |
Appl.
No.: |
10/784,201 |
Filed: |
February 24, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040167702 A1 |
Aug 26, 2004 |
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Foreign Application Priority Data
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Feb 24, 2003 [JP] |
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2003-046390 |
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Current U.S.
Class: |
701/301; 701/96;
340/903; 340/436 |
Current CPC
Class: |
B60T
17/221 (20130101); B60T 7/22 (20130101) |
Current International
Class: |
B60T
7/12 (20060101) |
Field of
Search: |
;701/93,96,300,301
;340/435,436,903 ;180/170,179 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A-09-081900 |
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Mar 1997 |
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JP |
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A-H10-338110 |
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Dec 1998 |
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JP |
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A-H11-139278 |
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May 1999 |
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JP |
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A-2001-030797 |
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Feb 2001 |
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JP |
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A-2002-347546 |
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Dec 2002 |
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JP |
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Other References
Notice of Rejection from Japanese Patent Office issued on Jan. 16,
2007 for the corresponding Japanese patent application No.
2003-046390 (a copy and English translation thereof). cited by
other.
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Primary Examiner: Chin; Gary
Attorney, Agent or Firm: Posz Law Group, PLC
Claims
What is claimed is:
1. A vehicle control system comprising: means for controlling a
running condition of a vehicle by setting a target control amount
based on a distance from the vehicle to an object present ahead of
the vehicle and relative speed with respect to said object present
ahead of the vehicle and accelerating or decelerating the vehicle
according to the target control amount; means for performing
control for avoiding a collision with the object if the collision
cannot be avoided by the control performed by the running condition
control means; and means for canceling an operation mode for
allowing the running condition control means to perform control if
control by the collision avoiding control means is activated when
the operation mode is active.
2. The vehicle control system according to claim 1, wherein the
target control amount is a target acceleration; the running
condition control means performs control with the target
acceleration limited to a limit acceleration that is preset to a
negative value if the target acceleration is smaller than the limit
acceleration; the collision avoiding control means performs control
with an avoidance acceleration that is smaller than the limit
acceleration at least at the start of activation thereof; and the
avoidance acceleration is set such that a perceivable difference to
the driver is generated between behaviors of the vehicle during
control by the running condition control means and during control
by the collision avoiding control means.
3. The control system according to claim 1, further comprising: a
control switch operable manually to initiate the operation mode of
the running condition control means, wherein the running condition
control means is enabled to perform the operation mode only by the
control switch when the operation mode of the running condition
control means is cancelled by the canceling means.
4. A vehicle control system comprising: means for controlling a
running condition of a vehicle by setting a target acceleration
based on a distance from the vehicle to an object present ahead of
the vehicle and relative speed with respect to said object present
ahead of the running vehicle and accelerating or decelerating the
vehicle according to the target acceleration; and means for
performing control for avoiding collision if a collision with the
object cannot be avoided by the control performed by the running
condition control means, wherein the running condition control
means performs actual control with the target acceleration limited
to a limit acceleration that is preset to a negative value if the
target acceleration is smaller than the limit acceleration; the
collision avoiding control means performs control with an avoidance
acceleration that is smaller than the limit acceleration at least
at the start of the control; and the avoidance acceleration is set
such that a perceivable difference to the driver is generated
between behaviors of the vehicle during control by the running
condition control means and during control by the collision
avoiding control means.
5. The vehicle control system according to claim 4, wherein the
difference between the limit acceleration and the avoidance
acceleration is at least one-tenth of gravity's acceleration.
6. The vehicle control system according to claim 5, further
comprising: alarm means for generating an alarm when the
possibility is high that the collision avoiding control means is
activated.
7. The vehicle control system according to claim 6, further
comprising: means for inhibiting operation of the collision
avoiding control means if a specified operation indicating that no
control by the collision avoiding control means is necessary is
detected in a period after activation of the alarm means and before
activation of the collision avoiding control means.
8. The vehicle control system according to claim 7, wherein the
specified operation is an operation of an accelerator pedal or a
specified switch.
9. The vehicle control system according to claim 6, further
comprising: second inhibiting means for inhibiting operation of the
collision avoiding control means when the possibility is low that
the object is a vehicle or when an object detecting device exhibits
low detecting accuracy.
10. The vehicle control system according to claim 9, further
comprising: means for enabling operation of the collision avoiding
control means only when an object, a collision with which is to be
avoided, has been an object of control by the running condition
control means for a preset monitoring time or more.
11. A vehicle control system comprising: means for controlling a
running condition of a vehicle by setting a target control amount
based on a distance from the vehicle to an object present ahead of
the vehicle and relative speed with respect to said object present
ahead of the vehicle and accelerating or decelerating the vehicle
according to the target control amount; means for performing
control for avoiding collision if a collision with the object
cannot be avoided by the control performed by the running condition
control means; means for generating an alarm when the possibility
is high that the collision avoiding control means is activated; and
means for inhibiting operation of the collision avoiding control
means if a specified operation indicating that no control by the
collision avoiding control means is necessary is detected in a
period after activation of the alarm means and before activation of
the collision avoiding control means.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon, claims the benefit of priority of,
and incorporates by reference Japanese Patent Applications No.
2003-46390 filed Feb. 24, 2003.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle control system for
controlling running conditions, such as running speed and
inter-vehicle distance, particularly for the purpose of avoiding a
collision on the basis of the distance from or relative speed with
respect to an object ahead of a vehicle.
2. Description of the Related Art
Conventionally, this type of vehicle control system is known as an
Adaptive Cruise Control (ACC) that detects a preceding vehicle as
an obstacle ahead of a vehicle, automatically controls the engine,
gears, and brakes of the vehicle to provide a target acceleration
that is determined on the basis of the distance from and relative
speed with respect to the preceding vehicle, and the running
condition of the vehicle. This makes it possible to properly
maintain the distance from the preceding vehicle.
The ACC system typically has a limited maximum deceleration
(minimum acceleration) that can be used in braking a vehicle for
assuring safety of passengers. However, in some instances, even
control at that maximum deceleration will not be able to avoid a
collision with a preceding vehicle. For this reason, various
control devices to be used in conjunction with an ACC system have
been proposed for avoiding collision, including, for example, a
device for signaling an alarm to a driver to prompt him or her,
that is, to the person driving the vehicle, to intervene when it is
determined that his or her vehicle is dangerously too close to a
preceding vehicle (see Japanese Patent Laid-Open Publication No.
2000-177429); and a device adapted such that braking force
generated when a driver intervenes and operates a brake is greater
than a normal braking force for helping to avoid a collision (see
Japanese Patent Laid-Open Publication No. Hei 11-139278). Further,
other devices have also been proposed, which are not used with an
ACC system, that detect a possibility of colliding with a preceding
vehicle and automatically decrease vehicle speed by generating an
acceleration (or deceleration) capable of avoiding the collision
(see Japanese Patent Laid-Open Publication No. Hei 10-338110).
By combining these techniques, it will be possible to envision a
control device for avoiding collision, which is used in conjunction
with an ACC system, and which, when it is determined that a maximum
deceleration of the ACC system is not sufficient to avoid a
collision with a preceding vehicle, automatically decreases the
vehicle speed by generating a deceleration (or negative
acceleration) larger than the maximum deceleration.
However, using this type of device that automatically performs
control for avoiding collision in addition to an ACC system, when a
vehicle is in a potential collision state, the driver will not even
be aware of this fact. Even if the driver is aware, the driver may
not bother to intervene in the control, overestimating the effect
of the device. These devices are merely for supporting drivers and,
without the drivers' intervening in the control, will increase
various risks all the more.
Specifically, these conventional control devices may not be able to
avoid collision, even after performing any necessary control,
depending upon the behavior of a preceding vehicle (e.g. abrupt
deceleration) or the condition of the road surface (e.g.
ice-covered road surface). Furthermore, if a sensor for detecting
the preceding vehicle or obstacle makes a false detection, the
control device will perform control for avoiding collision with
something like an object on the street side that in fact poses no
risk of collision, and will increase the risk of being rear-ended
by a following vehicle.
In addition, ACC systems are mostly designed to suppress
acceleration or deceleration if an object detected by a sensor is
possibly not a vehicle, or if an object detected by a sensor is a
vehicle but possibly is not correctly detected. In a case when the
ACC system performs such suppression and at the same time a similar
suppression is performed by an associated control device for
avoiding a collision, it will not be possible to avoid collision
with the detected object which is truly a vehicle.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to overcome
the aforementioned problems by enhancing the safety of driving by
adapting a vehicle control system for activating collision avoiding
control when collision with a preceding vehicle cannot be avoided
by normal running condition control, such that, when a vehicle is
in an emergency where the collision avoiding control is activated,
the driver is reliably prompted to intervene in the control.
In the vehicle control system according to the present invention
made for achieving the aforementioned object, a running condition
control means controls the running condition of a vehicle by
setting a target control amount based on a distance from and
relative speed with respect to an object present ahead of the
vehicle and accelerating or decelerating the vehicle according to
the target control amount. If collision with the object cannot be
avoided by the control performed by the running condition control
means, the collision avoiding control means performs control for
avoiding such collision.
The term "running condition" used herein at least includes running
speed or inter-vehicle distance (or inter-vehicle time).
Hereinafter, the control performed by the running condition control
means is also referred to as running condition control, and the
control performed by the collision avoiding control means is also
referred to as collision avoiding control. If collision avoiding
control is performed when an operation mode for performing running
condition control is active, a cancel means cancels the operation
mode.
According to the present invention, therefore, if collision
avoiding control is performed during running condition control, the
system will not automatically return to the running condition
control but the driver is inevitably obliged to operate the
vehicle. As a result, it is possible to prevent the driver from
being excessively dependent on the control system and failing to
intervene in the control (e.g. by operating the brake, etc.),
expecting that collision avoiding control will be performed
automatically, even though aware of a dangerous situation. If the
driver is not aware of the dangerous situation, it is possible to
alert the driver that the driver's vehicle is in such a dangerous
situation that the collision avoiding control is activated. As a
result, the driver's intervention in the control (operation of the
brake) is called for in an early stage, so that the dangerous
situation where the collision avoiding control is performed
repeatedly is not neglected, and hence the safety of driving can be
enhanced.
In the case where the running condition control means is designed
such that when a target acceleration is smaller than an
acceleration limit preset to a negative value, control is performed
with the target acceleration limited to the acceleration limit. It
is desirable that the collision avoiding control means is designed
to perform control with an avoidance acceleration that is smaller
than the acceleration limit at least at the start of activation,
and that the avoidance acceleration is set such that a difference
perceivable to the driver is generated between the behaviors of the
vehicle during the running condition control state and during the
collision avoiding control state. It is also desirable that a
difference between the acceleration limit and the avoidance
acceleration is specifically at least one-tenth of gravity's
acceleration.
In this manner, by establishing an appropriate difference between
the limit acceleration of the running condition control mode and
the avoidance acceleration of the collision avoiding control mode,
it is possible, beyond the limitation of the running condition
control, to cause the driver to inevitably recognize that the
collision avoiding control has started. When the system is provided
with the aforementioned cancel means in particular, it is possible
to cause the driver to recognize the reason why the running
condition control has been canceled automatically.
Further, when there is a high possibility that the collision
avoiding control means is activated, alarm means may generate an
alarm. In this case, the system may be designed such that an
inhibiting means inhibits operation of the collision avoiding
control means when a specific operation indicating that control by
no collision avoiding control means is necessary is detected in a
period after the activation of the alarm means and before the
activation of the collision avoiding control means. Thus, if the
driver's will to operate the vehicle is expressed by the specific
operation, the possibility is high that the detected object is
false and not a preceding vehicle. According to the present
invention, it is thus possible to prevent unnecessary collision
avoiding control for such false objects that might activate the
system and increase the risk of colliding with a following
vehicle.
Further, particularly when the system is provided with the
aforementioned cancel means, it is possible to prevent the running
condition control from being canceled as a result of erroneous
activation of the collision avoiding control, and hence from
bothering the driver due to the unnecessary canceling. The specific
operation may be operation of the accelerator peal or manipulation
of a specified switch. When the possibility is low that the
detected object is a vehicle, or when a device for detecting an
object has low accuracy, a second inhibiting means may be provided
for inhibiting the operation of the collision avoiding control
means.
In this case, it is possible to reliably prevent the collision
avoiding control from being activated for the detected object that
is not a vehicle, and even if the object is really a preceding
vehicle, minimum necessary processing, namely prompting the
driver's intervention, is ensured by activation of the alarm means.
Still further, in order to prevent the collision avoiding control
from being activated for a false object, an enabling means may be
provided for enabling the operation of the collision avoiding
control means only when an object collision, which is to be
avoided, has been an object of control by the running condition
control means for a period of time equal to or more than a preset
monitoring time.
Further areas of applicability of the present invention will become
apparent from the detailed description provided hereinafter. It
should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description and the accompanying drawings, wherein:
FIG. 1 is a block diagram schematically illustrating an adaptive
cruise control (ACC) system;
FIG. 2 is a flow chart showing the main processing performed by an
inter-vehicle distance ECU;
FIG. 3 is a flow chart showing a collision alarm determination
routine;
FIG. 4 is a flow chart showing a collision avoiding control
determination routine;
FIG. 5 is a state transition diagram showing the processing
performed in state transition or state response; and
FIG. 6 is a graph of acceleration required for avoiding collision
and state transitions.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiments is merely
exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
FIG. 1 is a block diagram schematically illustrating an adaptive
cruise control (ACC) system according to the present embodiment. As
shown in FIG. 1, the ACC system comprises an inter-vehicle distance
electronic control unit (hereinafter to be called "inter-vehicle
distance ECU") 2, an engine electronic control unit (hereinafter to
be called "engine ECU") 3, a brake electronic control unit
(hereinafter to be called "brake ECU") 4, and a meter electronic
control unit (hereinafter to be called "meter ECU") 5, which are
mutually connected via a LAN communication bus. The ECUs 2, 3, 4,
and 5 each employ a well-known microcomputer as a main component
and comprise at least a bus controller for performing
communications via the LAN communication bus. In the present
embodiment, data communications between the ECUs are conducted via
the LAN communication bus, using CAN ("Controller Area Network" by
Robert Bosch GmbH in Germany) protocol that is commonly utilized by
an on-vehicle network.
The inter-vehicle distance ECU 2 is also connected to a radar
sensor 6, an alarm buzzer 7, a cruise control switch 8, and a
target inter-vehicle distance setting switch 9. The radar sensor 6,
constructed as a laser radar sensor, is an electronic circuit
comprising, as principal components, a scanning range finder using
laser light and a microcomputer.
Scanning laser light is directed by the scanning range finder
within a predetermined angular range in the direction of a vehicle
width, so that attribute information representing attributes of an
object (whether the object is a vehicle, non-vehicle, or unknown)
and a probability that the object is present on the vehicle's own
lane (hereinafter to be called "own lane probability") are
determined based on a distance from and angle with respect to the
object detected by the reflected light, a current vehicle speed and
estimated radius of curvature radius of a curve (hereinafter to be
called "estimated R") received from the inter-vehicle distance ECU
2 and the like. At the same time, a collision flag is set for an
object approaching the driver's vehicle. The own lane probability,
attribute information and collision flag are sent to the
inter-vehicle distance ECU 2 as preceding vehicle information that
also includes information on the distance, relative speed and so
on. A diagnosis signal of the radar sensor 6 itself is also sent to
the inter-vehicle distance ECU 2. Alternatively, electric waves
(e.g. millimeter waves) may be used as radar waves in place of the
laser light.
The cruise control switch 8 comprises a main switch for
activating/stopping the inter-vehicle distance ECU 2, a set switch
for starting the inter-vehicle distance control described below, a
cancel switch for terminating the inter-vehicle distance control,
an accelerator lever for increasing a stored set speed, and a coast
lever for decreasing the set speed.
The target inter-vehicle distance setting switch 9 is a switch in
the ACC system manipulated by a driver for setting a time period
required by the driver's vehicle to travel a distance corresponding
to a target inter-vehicle distance between the driver's vehicle and
a preceding vehicle (hereinafter to be called "target inter-vehicle
time"). The target inter-vehicle time can be set within a
predetermined range.
The engine ECU 3 then transmits to the inter-vehicle distance ECU 2
a current vehicle speed, a pedal (accelerator) state signal
indicating the state of manipulation of the accelerator pedal, and
a control state (idling) signal indicating whether or not the
engine is in the idling state, based on sensor signals received
from a speed sensor 10 for detecting a vehicle speed, an
accelerator pedal opening sensor 11 for detecting an accelerator
pedal opening, and a throttle opening sensor (not shown). On the
other hand, the engine ECU 3 receives from the inter-vehicle
distance ECU 2 an inter-vehicle distance in-control flag indicating
whether the ACC system is active or not, a target acceleration, a
brake request, a diagnosis signal or the like, then determines a
driving state based on the information thus received, and in
accordance with the determined driving state, outputs a drive
command to an electronic throttle 12 or the like for adjusting an
engine throttle opening.
The brake ECU 4 transmits to the inter-vehicle distance ECU 2 a
steering angle received from a steering sensor 13 for detecting a
steering angle of the vehicle and a yaw rate received from a yaw
rate sensor 14 for detecting a yaw rate representing a turning
state of the vehicle, as well as a pedal state (brake) signal from
a brake pedal effort sensor 15 for detecting a state where a brake
pedal is depressed. On the other hand, the brake ECU 4 receives,
from the inter-vehicle distance ECU 2, an inter-vehicle distance
in-control flag, a target acceleration, a brake request and so on,
then determines a driving state based on the information thus
received, and in accordance with the determined driving state,
outputs a drive command to a brake actuator 16 or the like that
controls a W/C pressure of a brake hydraulic circuit for
controlling a braking force.
The meter ECU 5 receives, via the LAN communication bus,
information on various states of a vehicle, including vehicle
speed, engine speed, door open/close state, and transmission shift
range, and displays these items of information on a meter display
(not shown). Also, the meter ECU 5 receives, from the inter-vehicle
distance ECU 2, an inter-vehicle distance in-control flag, a
collision alarm, a diagnosis signal and so on, and displays these
items of information on a heads-up display 17 or the like.
The inter-vehicle distance ECU 2 receives information on the
current vehicle speed (Vn), engine control state, and pedal state
(accelerator) from the engine ECU 3, and receives information on
steering angle (str-eng, S0), yaw rate, pedal state (brake) and
soon from the brake ECU 4. The inter-vehicle distance ECU 2
determines a preceding vehicle to be the target of the ACC based on
the "own lane probability" included in the preceding vehicle
information received from the radar sensor 6, and sends an
inter-vehicle distance in-control flag to the respective ECUs 3, 4,
and 5 based on detection signals from the cruise control switch 8
and target inter-vehicle distance setting switch 9. At the same
time, the inter-vehicle distance ECU 2 transmits, as control
command values for proper adjustment of distance from the preceding
vehicle, the target acceleration, brake request, diagnosis signal
and the like to the engine ECU 3, the target acceleration, brake
request, and the like to the brake ECU 4, and the collision alarm,
diagnosis signal and soon to the meter ECU 5. Further, the
inter-vehicle distance ECU 2 determines whether or not an alarm is
to be generated, and if necessary activates the alarm buzzer 7.
Next, main processing performed by the inter-vehicle distance ECU 2
will be described with reference to the flow chart in FIG. 2.
First, radar data including preceding vehicle information is
received from the radar sensor 6 (S100), and successively CAN data
including a current vehicle speed (Vn), engine control state
(idling), pedal state (accelerator or brake), steering angle
(str-eng, S0), yaw rate and so on are received from the engine ECU
3 and brake ECU 4 (S200).
Then, an estimated R representing the traveling direction of the
vehicle is calculated based on the steering angle, yaw rate and
current vehicle speed acquired in S200, and an object (i.e. a
preceding vehicle) to be the object of control is selected based on
the own lane probability and attribute information based on radar
data and the like acquired in S100 (S300). Specifically, an object
that is closest to the vehicle is selected as a preceding vehicle
from among detected objects which have a certain level of
probability of being present in the vehicle's lane, and attribute
information indicating that the object is a vehicle or unknown.
Further, a target acceleration Ga is determined based on a distance
from and relative speed with respect to the preceding vehicle
selected in S300, attribute information of the preceding vehicle,
and a target inter-vehicle distance set by the target inter-vehicle
distance setting switch 9 (S400).
More specifically, if no preceding vehicle has been selected in
S300, a target acceleration Ga is determined such that the vehicle
is driven at a constant speed set by the manipulation of the
accelerator lever or coast lever. On the other hand, if a preceding
vehicle has been selected in S300, a target acceleration Ga is
determined by using a preset control map with an inter-vehicle
distance difference ratio and a relative speed with respect to the
preceding vehicle used as parameters.
Here, an inter-vehicle distance difference ratio (%) is obtained by
subtracting a target inter-vehicle distance set by the target
inter-vehicle distance setting switch 9 from a current
inter-vehicle distance to obtain an inter-vehicle distance
difference, dividing this inter-vehicle distance difference by the
target inter-vehicle distance, and multiplying the resultant
quotient by 100. However, the control map is set such that the
target acceleration Ga becomes greater as the inter-vehicle
distance difference ratio is greater. It should be noted that a
maximum value Gamax (0.5 m/s2 in the present embodiment) and a
minimum value Gamin (-2 m/s2 in the present embodiment) are set for
the target acceleration Ga and the control map is set such that the
target acceleration Ga is within the range between these values.
The relative speed used for this processing is processed by a
low-pass filter for suppressing variation in values due to
measurement error.
Then, an acceleration required for avoiding collision Gr (m/s2) is
determined by the following equation (1) based on a distance from
the preceding vehicle D (m), a relative speed V (m/s) and an
acceleration of the preceding vehicle A (m/s2) (S500).
Gr=A-V2/(2.times.(D-Dfin)) (1)
Here, Dfin denotes a minimum distance to be maintained (2 meters in
the present embodiment). In other words, the acceleration required
for avoiding collision Gr is an acceleration that makes the
relative speed V zero when the relative distance with respect to
the preceding vehicle reaches Dfin.
After that and onwards, determination about collision alarm (S600),
determination about collision avoiding control (S700), and state
transition and state response processing (S800) are carried out by
using the radar data and CAN data received in S100 and S200, and
the target acceleration Ga and acceleration required for avoiding
collision Gr obtained in S400 and S500. These processings will be
described later more particularly.
Thereafter, CAN data including the target acceleration, brake
request, diagnosis signal, and display data are sent to the engine
ECU 3, brake ECU 4, and meter ECU 5 (S900) and data including the
current vehicle speed (Vn) and estimated R are sent to the radar
sensor 6 (S1000). Thus the main processing of the inter-vehicle
distance ECU ends.
Particulars of the processings of S500 through S700 will be
described sequentially below. In the determination about collision
alarm performed in S600, as shown in the flow chart of FIG. 3, it
is determined in the first place if the collision alarm flag XA,
that is set for generating a collision alarm, is set to 1 (S601),
and if it is not set to 1, the following processings are performed
to determine whether or not conditions for generating a collision
alarm are established (S602 through S606).
More particularly, it is sequentially determined whether a
preceding vehicle has been selected in S300 (S602), whether the
selected preceding vehicle has been selected continuously for a
preset monitoring time T1 or more (5 seconds in the present
embodiment) (S603), whether the driver's vehicle is approaching the
preceding vehicle (relative speed R is less than 0) (S604), and
whether the acceleration required for avoiding collision Gr
obtained in S500 is smaller than the minimum value Gamin of the
target acceleration Ga, or whether collision cannot be avoided by a
normal inter-vehicle distance control in which the target
acceleration Ga is limited (S605). If any one of the determinations
is negative, that is, if any one of the conditions is met: a
preceding vehicle has not been selected, the preceding vehicle has
not been continuously selected for the monitoring time T1 or more,
R.gtoreq.0, or Gr.gtoreq.Gamin, then the processing ends without
setting the collision alarm flag XA.
On the other hand, if the determinations in S602 through S605 are
all positive, that is, if all of the conditions are met: a
preceding vehicle has been selected, the preceding vehicle has been
continuously selected for the monitoring time T1 or more, R<0,
and Gr<Gamin, then the collision alarm flag XA is set to 1
(S606) and the processing ends.
If it is determined that the collision alarm flag XA is set to 1 in
S601, then the following processings will be performed to determine
whether conditions for canceling the collision alarm mode are
established (S607 through S611).
More particularly, it is determined sequentially whether a
preceding vehicle has been selected in S300 (S607), whether the
state where the collision alarm flag XA is set to 1 has continued
for a preset minimum duration time T2 or more (1 second in the
present embodiment) (S608), whether the driver's vehicle is
approaching the preceding vehicle (relative speed R is less than
zero) (S609), and whether the acceleration required for avoiding
collision Gr obtained in S500 is equal to or greater than a value
obtained by adding a predetermined value Gaoff (0.5 m/s2 in the
present embodiment) to the minimum value Gaoff of the target
acceleration Ga.
If it is determined that a preceding vehicle has not been selected
in S607, or if it is determined that a preceding vehicle is
selected in S607 and both of the conditions are met in S608 and
S609: the state of XA=1 has continued for a grace period T2 or
more, and the driver's vehicle is not approaching the preceding
vehicle, or if all the conditions are met in S608 through S610: the
state of XA=1 has continued for a grace period T2 or more, the
driver's vehicle is approaching the preceding vehicle, and
Gr.gtoreq.Gamin+Gaoff, then the collision alarm flag XA is reset to
0 (S611) and the processing ends.
On the other hand, if it is determined that a preceding vehicle has
been selected in S607, and it is determined in S608 through S610
that the duration time of XA=1 is less than the minimum duration
time T2, or that the driver's vehicle is approaching the preceding
vehicle and Gr<Gamin+Gaoff, then the processing ends without
setting the collision alarm flag XA.
In other words, in these processings, if the collision alarm flag
XA has been reset, it is determined whether or not the collision
alarm flag XA is set according to the acceleration required for
avoiding collision Gr only when the probability is high that the
selected preceding vehicle is actually existent and the driver's
vehicle is approaching the preceding vehicle. In the case when the
collision alarm flag XA has been set to 1, the collision alarm flag
XA is reset to 0 unconditionally if a preceding vehicle has not
been selected. However, if a preceding vehicle has been selected,
it is determined whether or not the collision alarm flag XA is
reset according to the acceleration required for avoiding collision
Gr only when the driver's vehicle is approaching the selected
preceding vehicle. The threshold value of the acceleration required
for avoiding collision Gr used for setting or resetting the
collision alarm flag XA has a hysteresis and is set such that once
the collision alarm flag XA is set, this set state will continue at
least for the minimum duration time T2 so far as the preceding
vehicle has been selected.
Next, in the determination about collision avoiding control to be
performed in S700, as shown in the flow chart of FIG. 4, it is in
the first place determined whether a collision avoiding control
flag XC set for performing a collision avoiding control is set to 1
(S701). If it is not so set, the following processings are
performed to determine whether the conditions for performing a
collision avoiding control are established (S702 through S706).
More particularly, it is sequentially determined whether the
attribute of the preceding vehicle selected in S300 is a vehicle
(S702), whether the collision flag for the preceding vehicle is set
to 1 (S703), whether the own lane probability of the preceding
vehicle is greater than a threshold value Pf (80% in the present
embodiment) enabling the determination that the possibility of the
preceding vehicle being present in the vehicle driver's own lane is
sufficiently high (S704), and whether the acceleration required for
avoiding collision Gr obtained in S500 is smaller than a
determination value Gc that is set to a value smaller than the
minimum value Gamin of the target acceleration Ga for attaining a
greater deceleration (Gc=Gamin-0.98 (m/s2) in the present
embodiment) (S705). It should be noted that this determination
value Gc corresponds to an avoidance acceleration in the present
invention, and the maximum value Gamin corresponds to a limit
acceleration in the present invention.
If any one of the determinations in S702 through S705 is negative,
more specifically, if any one of the conditions are met: the
attribute of the preceding vehicle is not a vehicle, the collision
flag is reset to 0, the own lane probability is equal to or less
than the threshold value Pf, or Gr.gtoreq.Gc, then the processing
ends here without setting the collision avoiding flag XC.
On the other hand, if all the determinations in S702 through S705
are positive, that is, if all the conditions are met: the attribute
of the preceding vehicle is a vehicle, the collision flag is set to
1, the own lane probability is larger than the threshold value Pf,
and Gr<Gc, then the collision avoiding control flag XC is set to
1 (S706) and the processing ends.
If it is determined that the collision avoiding control flag XC is
set to 1 in S701, the following processings are performed to
determine whether the conditions to cancel the collision avoiding
control are established (S707 through S711). Specifically, it is
sequentially determined whether the attribute of the preceding
vehicle selected in S300 is a vehicle (S707), whether the collision
flag for the preceding vehicle is set to 1 (S708), whether the own
lane probability of the preceding vehicle is equal to or less than
the threshold value Pf (S709), and whether the acceleration
required for avoiding collision Gr obtained in S500 is equal to or
greater than a value obtained by adding a predetermined value Gcoff
(0.5 m/s2 in the present embodiment) to the determination value Gc
(S710).
If it is determined in S607 through S610 that any of the conditions
is met: the attribute of the preceding vehicle is not a vehicle,
the collision flag is reset to 0, the own lane probability is equal
to or less than the threshold value Pf, or Gr.gtoreq.Gc+Gcoff, then
the collision avoiding control flag XC is reset to 0 (S711) and the
processing ends.
On the other hand, if it is determined in S607 through S610 that
all of the conditions are met: the attribute of the preceding
vehicle is a vehicle, the collision flag is set to 1, the own lane
probability is greater than the threshold value Pf, and
Gr<Gc+Gcoff, then the processing ends without setting the
collision avoiding control flag XC.
In other words, if collision avoiding control flag XC is reset, it
is determined whether the collision avoiding control flag XC is to
be set based on the acceleration required for avoiding collision Gr
only when the selected preceding vehicle is a vehicle present in
the vehicle's own lane and is approaching the driver's vehicle. If
the collision avoiding control flag XC is set to 1, the collision
avoiding control flag XC is reset to 0 unconditionally when the
preceding vehicle is not a vehicle, is not approaching the driver's
vehicle, or is not present in the vehicle driver's own lane, and it
is determined whether or not the collision avoiding control flag XC
is reset based on the acceleration required for avoiding collision
Gr only when none of these conditions is met. The threshold value
used for setting or resetting the collision avoiding control flag
XC is set to have a hysteresis.
Now, the state transition and state response processing performed
in S800 will be described. In this processing, the states that can
be transited include a "cancel" state and "in-control" state. The
"in-control" state can be further classified into three sub-states
of "in-control, inter-vehicle distance control", "in-control,
collision alarm," and "in-control, collision avoiding control"
sub-states.
A state transition is performed according to the state transition
diagram in FIG. 5 based on the collision alarm flag XA set in S600,
the collision avoiding control flag XC set in S700, and the pedal
state (accelerator or brake).
First, the "cancel" state (the inter-vehicle distance in-control
flag FC=0) is established immediately after the main switch is
turned on. When the set switch is turned on in this "cancel" state,
the state transits to "in-control, inter-vehicle distance control"
sub-state (the inter-vehicle distance in-control flag FC=1). This
means that an operation mode for performing the inter-vehicle
distance control is established.
In any of the three sub-states of the "in-control" state, the state
transition to the "cancel" state occurs whenever an operation of
the brake pedal is detected. This means that the operation mode for
performing the inter-vehicle distance control is canceled.
Next, when the collision alarm flag XA is set in the "in-control,
inter-vehicle distance control" sub-state of the "in-control"
state, the state transits to the "in-control, collision alarm"
sub-state.
In the "in-control, collision alarm" sub-state, the state
transition to the "in-control, inter-vehicle distance control"
sub-states occurs when the collision alarm flag XA is reset or an
operation of the accelerator is detected. It is desirable to
inhibit the determination concerning a collision alarm for a
predetermined time period in order to prevent the state from
transiting to the "in-control, collision alarm" sub-state again
immediately after the transition to the "in-control, inter-vehicle
distance control" sub-state. When the collision avoiding control
flag XC is set, the state transits to the "in-control, collision
avoiding control" sub-state.
In the "in-control, collision avoiding control" sub-state, the
state transits to the "cancel" state when the collision avoiding
control flag XC is reset or an operation of the accelerator pedal
is detected. Namely, it is ensured that the "in-control" state is
canceled whenever a transition to the "in-control, collision
avoiding control" sub-state has occurred.
As for the state response processing, when in the "in-control,
inter-vehicle distance control" sub-state, the inter-vehicle
distance ECU 2 generates a brake request after determining whether
or not the vehicle needs to be braked based on the target
acceleration Ga calculated in S400, and sends the target
acceleration Ga and the brake request to the engine ECU 3 and the
brake ECU 4.
The engine ECU 3 finds a throttle opening command value based on
the target acceleration Ga, and drives and controls the electronic
throttle 12 after determining whether or not a control is to be
performed based on the brake request. The brake ECU 4 finds a W/C
pressure command value based on the target acceleration Ga, and
controls the brake actuator 16 after determining whether or not
control is to be performed based on the brake request, so that
acceleration or deceleration can be performed in accordance with
the target acceleration Ga. Specifically, if an actual acceleration
is greater than the target acceleration (or an actual deceleration
is smaller than the target deceleration), a throttle opening
command value is obtained so as to close the throttle, and a W/C
pressure command value is obtained so as to increase the braking
force.
When in the "in-control, collision alarm" sub-state, the
inter-vehicle distance ECU 2 causes the alarm buzzer 7 to sound for
alerting the driver that there is a high possibility of the
collision avoiding processing being started in the near future, and
sends to the meter ECU 5 a signal indicating that a collision alarm
is being generated. The meter ECU 5 displays on the heads-up
display 17 a message to prompt the driver to operate the brake and
to thus intervene in the control and, at the same time, gives a
visual notice to the driver for allowing him or her to prepare for
deceleration by the collision avoiding control.
When in the "in-control, collision avoiding control" sub-state, the
inter-vehicle distance ECU 2 sets the acceleration required for
avoiding collision Gr obtained in S500 as target acceleration Ga
and performs similar processing to the processing performed when in
the "in-control, inter-vehicle distance control" sub-state.
In the present embodiment, the processing performed in the
"in-control, inter-vehicle distance control" sub-state corresponds
to running condition control means, the processing performed in the
"in-control, collision alarm" sub-state corresponds to alarm means,
and the processing performed in the "in-control, collision avoiding
control" sub-state corresponds to a collision avoiding control
means. The processing to transit the state from the "in-control,
collision alarm" sub-state to the "in-control, inter-vehicle
distance control" sub-state when an operation of the accelerator
pedal is detected corresponds to an inhibiting means, the
processing in S702 through S704 corresponds to a second inhibiting
means, and the processing in S603 corresponds to an enabling
means.
As seen from FIG. 6, in the ACC system thus constructed according
to the present invention, generation of a collision alarm is
started as soon as the acceleration required for avoiding collision
Gr becomes smaller than the minimum value Gamin of the target
acceleration Ga during an inter-vehicle distance control. If the
acceleration required for avoiding collision Gr then returns to a
value greater than the value of Gamin+Gaoff without reaching the
determination value Gc, the collision alarm mode is canceled and
the system returns to the inter-vehicle distance control mode.
However, if the time period required for returning to a value
greater than the value of Gamin+Gaoff is less than the minimum
duration time T2, the collision alarm mode is continued until the
minimum duration time T2 elapses. It should be noted that, though
it is not shown in the drawing, if an operation of the accelerator
pedal is detected during generation of a collision alarm, the
collision alarm mode will be immediately canceled and the system
returns to the inter-vehicle distance control mode.
On the other hand, if the acceleration required for avoiding
collision Gr becomes smaller than the determination value Gc during
generation of a collision alarm, the collision avoiding control is
started. When the acceleration required for avoiding collision Gr
then returns to a value greater than the value of Gc+Gcoff, the
system will not return to the inter-vehicle distance control or
collision avoiding control and the operation mode to perform these
controls is canceled.
As discussed above, the control system according to the present
embodiment is designed such that, after a collision avoiding
control has been performed, the system cancels the control mode
instead of automatically returning to the inter-vehicle distance
control mode and makes the driver to operate the vehicle.
Therefore, it is possible to make the driver aware of the fact that
the driver's vehicle is in a dangerous situation where the
collision avoiding control was required. As a result, the driver
will intervene in the control (by operating the brake) in an early
stage, and in such a dangerous situation that requires repeated
collision avoiding controls will not be permitted to continue
thereafter. This means that the safety of driving can be
improved.
Further, in the present embodiment, a large difference (0.98
m/s2=0.1 G) is established between the minimum value Gamin of a
target acceleration set in the inter-vehicle distance control and
the acceleration required for avoiding collision Gr for performing
a collision avoiding control, so that when a collision avoiding
control is started, the vehicle changes its behavior in such a
manner that the change is perceptible to the driver. Therefore, the
driver is inevitably made aware of the fact that the collision
avoiding control has been started, and thus made to recognize the
reason why the ACC is automatically canceled thereafter.
Further, the present embodiment is adapted such that a collision
alarm is generated before starting a collision avoiding control,
and if an operation indicating that no collision avoiding control
is necessary (e.g. operation of the accelerator pedal) is detected
at this point of time, the system returns to a normal inter-vehicle
distance control mode without performing the collision avoiding
control. In other words, if the driver's will to operate the
vehicle is expressed by a specific operation, the possibility will
be high that the detection of an object is false and a collision
avoiding control will not be necessary with respect to such falsely
detected object. Thus, it is possible to avoid increasing the risk
of collision with a following vehicle as a result of performing
such unnecessary collision avoiding control, and also to avoid
burdening the driver by obliging him/her to cancel the ACC after an
unnecessary collision avoiding control.
Further, the present embodiment is designed such that the
generation of a collision alarm and thus the activation of a
collision avoiding control are enabled only for an object
(preceding vehicle) that has been the object of control for a
period time equal to or longer than the monitoring time T1 during
the inter-vehicle distance control, and such that when the
possibility is low that the object of control is not a vehicle,
only the collision alarm is generated and the collision avoiding
control is not activated.
As a result, according to the present embodiment, it is possible to
prevent a collision avoiding control from being performed for an
object that has been falsely detected or that is not a vehicle.
Even if the object is really a vehicle, the minimum necessary
processing, namely prompting the driver to intervene in the
control, can be carried out reliably by generating the collision
alarm.
Although only one embodiment of the present invention has been
described in the above, the present invention is not limited
thereto but may be practiced or embodied in various other ways. For
example, in the embodiment as described above, the transition to
the "in-control, inter-vehicle distance control" sub-state occurs
when an accelerator pedal is operated in the "in-control, collision
alarm" sub-state, but the certain switch specified in advance may
be used instead of the accelerator pedal. Further, this state
transition may be even omitted.
Still further, in the embodiment as described above, the step S702
is provided as the second inhibiting means so that the collision
avoiding control is inhibited when the possibility is low that the
detected object is a vehicle. However, in addition to (or in place
of) this, the collision avoiding control may be inhibited when it
is determined that the detection accuracy of the radar sensor 6 is
lowered based on the diagnosis signal from the radar sensor 6 or
the like.
The description of the invention is merely exemplary in nature and,
thus, variations that do not depart from the gist of the invention
are intended to be within the scope of the invention. Such
variations are not to be regarded as a departure from the spirit
and scope of the invention.
* * * * *